1. Field of the Invention
The present invention relates to a mercury-containing material, a method for producing the same and a fluorescent lamp using the same.
2. Description of Related Art
In a conventional process for producing a fluorescent lamp, mercury is enclosed in the lamp in the following method. Stems having a filament and an exhaust pipe are sealed at the ends of a glass bulb whose inner surface is coated with a fluorescent substance. Subsequently, impurities are exhausted from the glass bulb through the exhaust pipe, and liquid mercury is enclosed in the glass bulb through the exhaust pipe immediately before finishing this exhaustion.
In order to enclose precisely a minimal amount of mercury, another known method of enclosing mercury in the fluorescent lamp includes enclosing a mercury alloy (a mercury-containing material) formed of, for example, mercury and zinc in the glass bulb through the exhaust pipe immediately before finishing exhausting the glass bulb.
The enclosed mercury alloy sometimes is fixed inside the glass bulb so as not to move freely therein.
However, in the conventional process for producing the fluorescent lamp, in particular, in the method of enclosing the liquid mercury directly in the glass bulb, there has been a problem that a predetermined amount of mercury cannot be enclosed. This is because a part of the liquid mercury adheres to a mercury enclosing apparatus or evaporates owing to heat during the exhaustion so as to be exhausted along with an impure gas.
In order to solve the above problem, there is a method of enclosing mercury in an amount somewhat larger than necessary in the glass bulb. However, it is not preferable, in practice, to enclose an excessive amount of mercury, which is unfriendly to the environment.
On the other hand, the method of enclosing the solid mercury alloy instead of the liquid mercury in the glass bulb has had problems that, when the mercury alloy is not fixed inside the fluorescent lamp, it collides against the fluorescent coating during a lamp transportation so as to make linear and pinhole-shaped flaws in the fluorescent coating and that such a collision makes a noise. There also has been a problem that, during a lamp operation, a dark shadow of the mercury alloy appears on the fluorescent lamp, thus deteriorating the appearance.
Also, even if the mercury alloy is fixed inside the fluorescent lamp in a production process, it comes off relatively easily because of an impact during the lamp transportation, leading to the various problems described above.
It is an object of the present invention to solve the problems described above and to provide a mercury-containing material, a method for producing the same and a fluorescent lamp using the same that can enclose a minimal amount of mercury in a glass bulb precisely, prevent flaws in a fluorescent coating while suppressing a noise during lamp transportation, and prevent deterioration in appearance.
A mercury-containing material of the present invention includes liquid mercury, and a continuous film with which a surface of the liquid mercury is coated.
With this structure, since the liquid mercury is coated with the continuous film, the mercury can be prevented from, as seen conventionally, adhering to the enclosing apparatus and evaporating to be exhausted during an exhausting process. Thus, a minimal amount of mercury can be enclosed precisely in a fluorescent lamp. Also, since the continuous film is flexible, it is possible to suppress flaws and noises caused by a collision of this continuous film against a fluorescent coating of the fluorescent lamp. Moreover, since the continuous film is thin so as to have a large light transmittance, a shadow of the continuous film can be prevented from being cast on the fluorescent lamp during lamp operation.
In the mercury-containing material, the continuous film is made of at least one material selected from the group consisting of a metal oxide and a metal complex oxide. With this structure, it is possible to prevent a reaction between a substance forming the continuous film and an activated mercury ion during the lamp operation, leading to a decrease in mercury contributing to a discharge.
It is preferable that the continuous film has a thickness of 0.1 to 1.0 mm. This is because a continuous film having a thickness of smaller than 0.1 mm would break during handling in the producing process, while that having a thickness of larger than 1.0 mm would be difficult to break when it should be broken intentionally.
Also, it is preferable that the continuous film is formed by layering a plurality of thin films. With this structure, since an amount of a continuous film forming solution smaller than the amount required for forming a thick continuous film at one time sufficiently can be made adhere to the surface of the mercury, it is possible to reduce the amount of heat necessary in a heating process. Consequently, impurities contained in the continuous film forming solution are not absorbed in the continuous film owing to an abrupt heating, so that these impurities would not affect the lamp characteristics adversely.
It is preferable that an innermost thin film of the thin films constituting the continuous film is thinnest. With this structure, it is possible to reduce the amount of heat applied to the continuous film forming solution in the process of forming the first thin film (continuous film). As a result, the amount of heat applied to the solid mercury can be reduced, thereby suppressing the evaporation of the mercury and increasing the accuracy of the enclosed mercury amount.
Furthermore, it is preferable that the mercury-containing material is a spherical body. With this structure, the mercury-containing material can be enclosed in the fluorescent lamp easily.
The mercury-containing material preferably is obtained by making a metal alkoxide solution adhere onto a surface of mercury and heating the metal alkoxide solution on the surface of the mercury. This is because the mercury-containing material obtained in this method has a minimal amount of the mercury coated with the continuous film and a substantially spherical shape that allows easy enclosure into the fluorescent lamp. In addition, since the continuous film is flexible, the mercury-containing material does not damage the fluorescent coating and the lamp has an excellent appearance when the mercury-containing material is enclosed.
Next, a method for producing a mercury-containing material of the present invention, wherein a continuous film is formed on a surface of mercury by (a) dipping the mercury in a continuous film forming solution so as to make the continuous film forming solution adhere onto the surface of the mercury, and (b) heating the continuous film forming solution on the surface of the mercury.
With this method, it is possible to cut waste so as to coat a minimal amount of the mercury with the continuous film. Furthermore, it is possible to form the mercury-containing material into a shape that allows easy enclosure into the fluorescent lamp, that is, a substantially spherical shape.
In the above-described method for producing the mercury-containing material, a solidified mercury, in particular a mercury obtained by solidifying liquid mercury in a noble gas atmosphere, preferably is used as the mercury.
With this method, because the mercury is solidified in advance, it is possible to further eliminate waste so as to coat a minimal amount of the mercury with the continuous film and the handling of the mercury becomes easier when forming the continuous film. Also, by solidifying the liquid mercury in the noble gas atmosphere, it is possible to prevent impure gases (such as oxygen and nitrogen), which affect characteristics of the fluorescent lamp adversely, from being absorbed in the continuous film on the surface of the liquid mercury during the solidification.
In the above-described method for producing the mercury-containing material, it is preferable that a metal alkoxide solution is used as the continuous film forming solution. With this method, it is possible to form the continuous film on the surface of the mercury relatively easily so as to coat a minimal amount of the mercury with continuous film. Furthermore, it is possible to form the mercury-containing material into a shape that allows easy enclosure into the fluorescent lamp, that is, a substantially spherical shape.
In the above-described method for producing the mercury-containing material, it is preferable that a mixed gas of a natural gas and oxygen is used for (b). With this method, since the mixed gas of the natural gas and oxygen does not generate very much moisture at the time of burning, it is possible to prevent the continuous film from absorbing the moisture, thereby reducing an adverse effect on the lamp characteristics caused by the moisture absorption.
In the above-described method for producing the mercury-containing material, it is preferable that a mixed gas of a town gas and oxygen is used for (b). With this method, since the mixed gas of the town gas and oxygen does not generate very much moisture at the time of burning, it is possible to prevent the continuous film from absorbing the moisture, thereby reducing an adverse effect on the lamp characteristics caused by the moisture absorption.
Next, a fluorescent lamp of the present invention includes a glass bulb, in which an enclosed gas and the mercury-containing material are sealed, and a fluorescent coating formed on an inner surface of the glass bulb.
With this structure, a minimal amount of mercury precisely can be enclosed in the fluorescent lamp. Also, since the continuous film is flexible, it is possible to prevent a flaw on the fluorescent coating and a noise that are due to a collision of this continuous film against the fluorescent coating of the fluorescent lamp. Moreover, since the continuous film is thin, the shadow of the continuous film is unlikely to appear on the fluorescent lamp during the lamp operation.